The invention relates to pressure-sensitive adhesive products for use in adhering to skin or like delicate surfaces.
Pressure-sensitive adhesive tapes and the like are used in a wide variety of applications where there is a need to adhere to skin, for example, medical tapes such as wound or surgical dressings, athletic tapes, surgical drapes, or tapes or tabs used in adhering medical devices such as sensors, electrodes, ostomy appliances, or the like. A concern with all these adhesive coated products is the need to balance the objective of providing sufficiently high levels of wet and dry adhesion to ensure that the pressure-sensitive tape products do not fall off, while ensuring that the underlying skin experiences the least amount of trauma, damage, or irritation possible while the adhesive tape or the like is being used and/or removed. These goals are generally conflicting. Pressure-sensitive adhesives are known that are hypoallergenic in nature, minimizing allergic reactions. However, tape products using these adhesives can still damage or irritate skin. For example, lack of breathability can result in overhydration and sometimes maceration of the skin. Adhesives which tend to build in adhesion or have excessively high levels of initial adhesion can pull off skin cells or layers, particularly when the skin cells have lost some of their cohesion due to overhydration or maceration. These problems are particularly pronounced where tapes are repeatedly adhered to a given site. Each time a tape is removed, the underlying skin experiences a traumatic event removing further skin cells or layers, which damage can accumulate faster than the body can repair it. U.S. Pat. No. 5,614,310 addresses this problem by suggesting a particular adhesive layer formed using solvent-insoluble, solvent-dispersible, acrylate-based elastomeric pressure-sensitive adhesive microspheres optionally impregnated with an antimicrobial agent. The backing used with this adhesive preferably has a moisture vapor transmission rate (MVTR) value of at least 500 g/m2/day (measured using ASTM E 96-80 at 40xc2x0 C.). This adhesive showed low levels of adhesion build-up to skin over time. Although acceptable for some uses, this adhesive is somewhat difficult to manufacture, still exhibits some adhesion build-up to skin over time, can cause moisture build-up, and lacks high levels of cohesion which can result in adhesive transfer to skin.
Another approach in the art to providing pressure-sensitive tapes and the like with low levels of skin irritation and/or damage has been the use of pattern coated adhesives. A discontinuous adhesive coating on a backing allows the skin to breathe, at least in the areas of the backing not coated with adhesive. This approach is disclosed in U.S. Pat. No. 4,595,001 and U.S. Pat. No. 5,613,942, as well as EP 353972 and EP 91800. These patent documents generally teach intermittent coating of adhesives onto different backings. For example, U.S. Pat. No. 5,613,942 describes printing pressure-sensitive adhesives using a release coated calender roll process similar to Gravure printing. This patent also teaches screen printing. However, pattern coating or printing of adhesives in this manner is problematic as it generally requires solvents, which are environmentally problematic. Further, residual low molecular weight species can cause skin irritation. It would be preferred, from environmental, manufacturing (e.g., elimination of the need for expensive solvent recovery), and performance perspectives to have adhesives coatable directly from a melt phase.
EP Pat. Appln. No. 448213 addresses the problem of skin irritation by proposing coating the skin with retinoids either prior to applying the adhesive tape or by placing a retinoid layer on the adhesive layer itself. However, this conditioning barrier layer can also interfere with adhesion. Similarly, U.S. Pat. No. 4,140,115 teaches use of a specific conditioning additive to an adhesive to reduce stripping of skin cells upon removal of a tape. The adhesive mass contains an unreacted polyol in an amount ranging from 4 weight percent (wt-%) to 20 wt-%. However, the polyol also reduces the adhesion force.
U.S. Pat. No. 4,024,312 suggests the use of an elastomeric backing, which is stretched at a zero degree angle when removed, thereby resulting in the adhesive layer stretching and removing more easily. However, elastic tapes are difficult to handle and manufacture, adhesive tackifiers tend to migrate from the adhesive into the elastic backing, and it is difficult for the user to remember to remove the tape only in this one manner, which is different from how tapes are typically removed.
There remains a need for pressure-sensitive adhesive tapes, and the like, that exhibit low trauma and irritation to skin in use and upon removal, particularly repeated use on the same site, regardless of the manner of removal and which are easily made from hot melt applied pressure-sensitive adhesives.
There is also a need for pressure-sensitive adhesive tapes, and the like, that exhibit good adhesion to wet skin or like surfaces. Articles having good wet skin adhesion are described in U.S. Pat. No. 5,613,942. These articles include a porous backing made of non-wettable fibers and a discontinuously coated adhesive. The backing absorbs less than 4% by weight water, thereby allowing water on wet skin to pass through the entire article. Although this provides suitable wet skin adhesion, there is still a need for articles having even greater initial adhesion to wet skin or like surfaces, preferably, on the order of the same article""s initial adhesion to dry skin or like surfaces.
The invention relates to a low trauma pressure-sensitive adhesive coated substrate comprising a sheet material, tape, or laminate structure designed to adhere to skin or like surfaces. The pressure-sensitive adhesive layer of this adhesive coated substrate is a fibrous adhesive layer generally having a basis weight of from 5 g/m2 to 200 g/m2 applied to a conformable backing or substrate. The fibrous adhesive layer has a textured outer face and persistent porosity between discrete adhesive fibers. Generally, the fibrous adhesive layer has a MVTR measured by ASTM E 96-80 at 40xc2x0 C.) of at least 1000 g/m2/day, preferably at least 6000 g/m2/day.
In certain preferred low trauma embodiments, the present invention also relates to sheet materials, tapes, or laminate structures designed to adhere to wet skin, which are suitable for use as medical tapes and dressings, for example. Such embodiments include a backing substrate comprising an absorbent material in the form of a web or film. In such embodiments, the adhesive coated substrate has an initial dry skin adhesion of at least 20 g/2.5 cm (0.08 N/cm), an initial wet skin adhesion of at least 20 g/2.5 cm (0.08 N/cm), and preferably, an initial wet skin adhesion that is at least about 65% of the initial dry skin adhesion.
In other embodiments, the present invention provides an adhesive coated substrate comprising a backing substrate and a fibrous adhesive layer comprising an entangled web of pressure-sensitive adhesive fibers, wherein the backing substrate comprises an absorbent material in the form of a web or film, and further wherein the adhesive coated substrate has an initial dry skin adhesion of at least 20 g/2.5 cm (0.08 N/cm), an initial wet skin adhesion of at least 20 g/2.5 cm (0.08 N/cm), and an initial wet skin adhesion that is at least about 65% of the initial dry skin adhesion.